The present invention relates to the field of radiologic imagery which makes it possible to visualize an organ or an organ part, in general of the human body.
Conventionally, X-ray radiography has been performed by means of sensitized films acted upon by X-rays after their passage through the organ to be studied. Radiologists have been trained in the interpretation of such images. Novel imagery technologiesxe2x80x94solid state detector and digital acquisition systemxe2x80x94must be adapted to current practice and must furnish an equivalent perception of pertinent information that radiologists have to examine. In particular, one of the requirements that digital systems must satisfy consists in an extension of the dynamics of gray level that simulates a conventional film as faithfully as possible. To that end, the digital image is displayed on a screen that the radiologist adjusts in interactive fashion to identify all the clinical signs in perceiving relations among the various components of the image. But the precise perception of density information by means of the image displayed on the screen is limited by the dynamics of the screen. Now one must automatically pass from the high contrast of the image of origin, for example in the region of 30 to 50, to the low contrast offered by a video screen.
Currently, physicians apply conformation techniques to patients with the aim of limiting the dynamics of acquired images, for example by compression of thick regions, and/or by addition of absorbent substances to compensate for zones of little thickness. In the case of X-ray mammography, the breast is compressed to the smallest and most constant thickness possible. In the field of cardiology, contour filters are used to avoid problems related to poorly absorbent zones of the chest, such as the lungs. These filters consist in plates of a shape complementary to that of the heart, made of materials of given coefficients of X-ray absorption.
However, these techniques prove to be inadequate for the acquisition and digital processing of images, and difficult to carry out.
The present invention will be understood better upon study of the detailed description and illustrated by the accompanying drawings, wherein:
The method of compensation for the thickness of an object, such as an organ is provided by an X-ray machine of the type containing a source of X-rays and a means of detection of the beam of X-rays after it has passed through the organ, the means of detection being capable of converting the X-ray beam into a digital electronic signal. From a digitized image, there is calculated an image of the radiologic thicknesses of the organ traversed by the X-ray beam, the thickness zero corresponding to the zones of the image without organ, a thickness threshold is defined, from this there is derived an algebraic compensation image making it possible to bring the pixels of lower or higher level back to the threshold to the value of the threshold, and the thickness image and a proportion of the compensation image are summed up, to obtain a compensated thickness image.
The compensation image is filtered through a low-pass filter, then through the mask, prior to summation of the images.
Thus, the invention provides an image processing method furnishing an image equivalent to that which would be obtained by arranging an absorbent liquid on the edges of the organ over a part of their height and makes it possible to simulate a physical phenomenon which furnishes a better understanding of the optimal adjustment of the parameters that must be effected. This image processing gives the organ studied a natural and pleasant appearance. The method is easy to carry out by the adaptation of existing digital X-ray machines and may be applied to the radiography of any organ whatsoever.